4
a,
/ [tex]\underset{AM}{\rightarrow}-\underset{AN}{\rightarrow}= \underset{NM}{\rightarrow}[/tex] /
/ [tex]\underset{MN}{\rightarrow}-\underset{PN}{\rightarrow}= \underset{MP}{\rightarrow}[/tex] /
/ [tex]\underset{BP}{\rightarrow}-\underset{CP}{\rightarrow}= \underset{BC}{\rightarrow}[/tex] /